/*  -- translated by f2c (version 20240504).
   You must link the resulting object file with libf2c:
	on Microsoft Windows system, link with libf2c.lib;
	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
	or, if you install libf2c.a in a standard place, with -lf2c -lm
	-- in that order, at the end of the command line, as in
		cc *.o -lf2c -lm
	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

		http://www.netlib.org/f2c/libf2c.zip
*/

#include "f2c.h"

/* > \brief \b DSYR2K   

    =========== DOCUMENTATION ===========   

   Online html documentation available at   
              http://www.netlib.org/lapack/explore-html/   

    Definition:   
    ===========   

         SUBROUTINE DSYR2K(UPLO,TRANS,N,K,ALPHA,A,LDA,B,LDB,BETA,C,LDC)   

         DOUBLE PRECISION ALPHA,BETA   
         INTEGER K,LDA,LDB,LDC,N   
         CHARACTER TRANS,UPLO   
         DOUBLE PRECISION A(LDA,*),B(LDB,*),C(LDC,*)   


   > \par Purpose:   
    =============   
   >   
   > \verbatim   
   >   
   > DSYR2K  performs one of the symmetric rank 2k operations   
   >   
   >    C := alpha*A*B**T + alpha*B*A**T + beta*C,   
   >   
   > or   
   >   
   >    C := alpha*A**T*B + alpha*B**T*A + beta*C,   
   >   
   > where  alpha and beta  are scalars, C is an  n by n  symmetric matrix   
   > and  A and B  are  n by k  matrices  in the  first  case  and  k by n   
   > matrices in the second case.   
   > \endverbatim   

    Arguments:   
    ==========   

   > \param[in] UPLO   
   > \verbatim   
   >          UPLO is CHARACTER*1   
   >           On  entry,   UPLO  specifies  whether  the  upper  or  lower   
   >           triangular  part  of the  array  C  is to be  referenced  as   
   >           follows:   
   >   
   >              UPLO = 'U' or 'u'   Only the  upper triangular part of  C   
   >                                  is to be referenced.   
   >   
   >              UPLO = 'L' or 'l'   Only the  lower triangular part of  C   
   >                                  is to be referenced.   
   > \endverbatim   
   >   
   > \param[in] TRANS   
   > \verbatim   
   >          TRANS is CHARACTER*1   
   >           On entry,  TRANS  specifies the operation to be performed as   
   >           follows:   
   >   
   >              TRANS = 'N' or 'n'   C := alpha*A*B**T + alpha*B*A**T +   
   >                                        beta*C.   
   >   
   >              TRANS = 'T' or 't'   C := alpha*A**T*B + alpha*B**T*A +   
   >                                        beta*C.   
   >   
   >              TRANS = 'C' or 'c'   C := alpha*A**T*B + alpha*B**T*A +   
   >                                        beta*C.   
   > \endverbatim   
   >   
   > \param[in] N   
   > \verbatim   
   >          N is INTEGER   
   >           On entry,  N specifies the order of the matrix C.  N must be   
   >           at least zero.   
   > \endverbatim   
   >   
   > \param[in] K   
   > \verbatim   
   >          K is INTEGER   
   >           On entry with  TRANS = 'N' or 'n',  K  specifies  the number   
   >           of  columns  of the  matrices  A and B,  and on  entry  with   
   >           TRANS = 'T' or 't' or 'C' or 'c',  K  specifies  the  number   
   >           of rows of the matrices  A and B.  K must be at least  zero.   
   > \endverbatim   
   >   
   > \param[in] ALPHA   
   > \verbatim   
   >          ALPHA is DOUBLE PRECISION.   
   >           On entry, ALPHA specifies the scalar alpha.   
   > \endverbatim   
   >   
   > \param[in] A   
   > \verbatim   
   >          A is DOUBLE PRECISION array, dimension ( LDA, ka ), where ka is   
   >           k  when  TRANS = 'N' or 'n',  and is  n  otherwise.   
   >           Before entry with  TRANS = 'N' or 'n',  the  leading  n by k   
   >           part of the array  A  must contain the matrix  A,  otherwise   
   >           the leading  k by n  part of the array  A  must contain  the   
   >           matrix A.   
   > \endverbatim   
   >   
   > \param[in] LDA   
   > \verbatim   
   >          LDA is INTEGER   
   >           On entry, LDA specifies the first dimension of A as declared   
   >           in  the  calling  (sub)  program.   When  TRANS = 'N' or 'n'   
   >           then  LDA must be at least  max( 1, n ), otherwise  LDA must   
   >           be at least  max( 1, k ).   
   > \endverbatim   
   >   
   > \param[in] B   
   > \verbatim   
   >          B is DOUBLE PRECISION array, dimension ( LDB, kb ), where kb is   
   >           k  when  TRANS = 'N' or 'n',  and is  n  otherwise.   
   >           Before entry with  TRANS = 'N' or 'n',  the  leading  n by k   
   >           part of the array  B  must contain the matrix  B,  otherwise   
   >           the leading  k by n  part of the array  B  must contain  the   
   >           matrix B.   
   > \endverbatim   
   >   
   > \param[in] LDB   
   > \verbatim   
   >          LDB is INTEGER   
   >           On entry, LDB specifies the first dimension of B as declared   
   >           in  the  calling  (sub)  program.   When  TRANS = 'N' or 'n'   
   >           then  LDB must be at least  max( 1, n ), otherwise  LDB must   
   >           be at least  max( 1, k ).   
   > \endverbatim   
   >   
   > \param[in] BETA   
   > \verbatim   
   >          BETA is DOUBLE PRECISION.   
   >           On entry, BETA specifies the scalar beta.   
   > \endverbatim   
   >   
   > \param[in,out] C   
   > \verbatim   
   >          C is DOUBLE PRECISION array, dimension ( LDC, N )   
   >           Before entry  with  UPLO = 'U' or 'u',  the leading  n by n   
   >           upper triangular part of the array C must contain the upper   
   >           triangular part  of the  symmetric matrix  and the strictly   
   >           lower triangular part of C is not referenced.  On exit, the   
   >           upper triangular part of the array  C is overwritten by the   
   >           upper triangular part of the updated matrix.   
   >           Before entry  with  UPLO = 'L' or 'l',  the leading  n by n   
   >           lower triangular part of the array C must contain the lower   
   >           triangular part  of the  symmetric matrix  and the strictly   
   >           upper triangular part of C is not referenced.  On exit, the   
   >           lower triangular part of the array  C is overwritten by the   
   >           lower triangular part of the updated matrix.   
   > \endverbatim   
   >   
   > \param[in] LDC   
   > \verbatim   
   >          LDC is INTEGER   
   >           On entry, LDC specifies the first dimension of C as declared   
   >           in  the  calling  (sub)  program.   LDC  must  be  at  least   
   >           max( 1, n ).   
   > \endverbatim   

    Authors:   
    ========   

   > \author Univ. of Tennessee   
   > \author Univ. of California Berkeley   
   > \author Univ. of Colorado Denver   
   > \author NAG Ltd.   

   > \ingroup her2k   

   > \par Further Details:   
    =====================   
   >   
   > \verbatim   
   >   
   >  Level 3 Blas routine.   
   >   
   >   
   >  -- Written on 8-February-1989.   
   >     Jack Dongarra, Argonne National Laboratory.   
   >     Iain Duff, AERE Harwell.   
   >     Jeremy Du Croz, Numerical Algorithms Group Ltd.   
   >     Sven Hammarling, Numerical Algorithms Group Ltd.   
   > \endverbatim   
   >   
    =====================================================================   
   Subroutine */ int igraphdsyr2k_(char *uplo, char *trans, integer *n, integer *k, 
	doublereal *alpha, doublereal *a, integer *lda, doublereal *b, 
	integer *ldb, doublereal *beta, doublereal *c__, integer *ldc)
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, c_dim1, c_offset, i__1, i__2, 
	    i__3;

    /* Local variables */
    integer i__, j, l, info;
    doublereal temp1, temp2;
    extern logical igraphlsame_(char *, char *);
    integer nrowa;
    logical upper;
    extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);


/*  -- Reference BLAS level3 routine --   
    -- Reference BLAS is a software package provided by Univ. of Tennessee,    --   
    -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--   


    =====================================================================   


       Test the input parameters.   

       Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    c_dim1 = *ldc;
    c_offset = 1 + c_dim1;
    c__ -= c_offset;

    /* Function Body */
    if (igraphlsame_(trans, "N")) {
	nrowa = *n;
    } else {
	nrowa = *k;
    }
    upper = igraphlsame_(uplo, "U");

    info = 0;
    if (! upper && ! igraphlsame_(uplo, "L")) {
	info = 1;
    } else if (! igraphlsame_(trans, "N") && ! igraphlsame_(trans, 
	    "T") && ! igraphlsame_(trans, "C")) {
	info = 2;
    } else if (*n < 0) {
	info = 3;
    } else if (*k < 0) {
	info = 4;
    } else if (*lda < max(1,nrowa)) {
	info = 7;
    } else if (*ldb < max(1,nrowa)) {
	info = 9;
    } else if (*ldc < max(1,*n)) {
	info = 12;
    }
    if (info != 0) {
	igraphxerbla_("DSYR2K", &info, (ftnlen)6);
	return 0;
    }

/*     Quick return if possible. */

    if (*n == 0 || (*alpha == 0. || *k == 0) && *beta == 1.) {
	return 0;
    }

/*     And when  alpha.eq.zero. */

    if (*alpha == 0.) {
	if (upper) {
	    if (*beta == 0.) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = j;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = 0.;
/* L10: */
		    }
/* L20: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = j;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1];
/* L30: */
		    }
/* L40: */
		}
	    }
	} else {
	    if (*beta == 0.) {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = *n;
		    for (i__ = j; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = 0.;
/* L50: */
		    }
/* L60: */
		}
	    } else {
		i__1 = *n;
		for (j = 1; j <= i__1; ++j) {
		    i__2 = *n;
		    for (i__ = j; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1];
/* L70: */
		    }
/* L80: */
		}
	    }
	}
	return 0;
    }

/*     Start the operations. */

    if (igraphlsame_(trans, "N")) {

/*        Form  C := alpha*A*B**T + alpha*B*A**T + C. */

	if (upper) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (*beta == 0.) {
		    i__2 = j;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = 0.;
/* L90: */
		    }
		} else if (*beta != 1.) {
		    i__2 = j;
		    for (i__ = 1; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1];
/* L100: */
		    }
		}
		i__2 = *k;
		for (l = 1; l <= i__2; ++l) {
		    if (a[j + l * a_dim1] != 0. || b[j + l * b_dim1] != 0.) {
			temp1 = *alpha * b[j + l * b_dim1];
			temp2 = *alpha * a[j + l * a_dim1];
			i__3 = j;
			for (i__ = 1; i__ <= i__3; ++i__) {
			    c__[i__ + j * c_dim1] = c__[i__ + j * c_dim1] + a[
				    i__ + l * a_dim1] * temp1 + b[i__ + l * 
				    b_dim1] * temp2;
/* L110: */
			}
		    }
/* L120: */
		}
/* L130: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		if (*beta == 0.) {
		    i__2 = *n;
		    for (i__ = j; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = 0.;
/* L140: */
		    }
		} else if (*beta != 1.) {
		    i__2 = *n;
		    for (i__ = j; i__ <= i__2; ++i__) {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1];
/* L150: */
		    }
		}
		i__2 = *k;
		for (l = 1; l <= i__2; ++l) {
		    if (a[j + l * a_dim1] != 0. || b[j + l * b_dim1] != 0.) {
			temp1 = *alpha * b[j + l * b_dim1];
			temp2 = *alpha * a[j + l * a_dim1];
			i__3 = *n;
			for (i__ = j; i__ <= i__3; ++i__) {
			    c__[i__ + j * c_dim1] = c__[i__ + j * c_dim1] + a[
				    i__ + l * a_dim1] * temp1 + b[i__ + l * 
				    b_dim1] * temp2;
/* L160: */
			}
		    }
/* L170: */
		}
/* L180: */
	    }
	}
    } else {

/*        Form  C := alpha*A**T*B + alpha*B**T*A + C. */

	if (upper) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = j;
		for (i__ = 1; i__ <= i__2; ++i__) {
		    temp1 = 0.;
		    temp2 = 0.;
		    i__3 = *k;
		    for (l = 1; l <= i__3; ++l) {
			temp1 += a[l + i__ * a_dim1] * b[l + j * b_dim1];
			temp2 += b[l + i__ * b_dim1] * a[l + j * a_dim1];
/* L190: */
		    }
		    if (*beta == 0.) {
			c__[i__ + j * c_dim1] = *alpha * temp1 + *alpha * 
				temp2;
		    } else {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1] 
				+ *alpha * temp1 + *alpha * temp2;
		    }
/* L200: */
		}
/* L210: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = *n;
		for (i__ = j; i__ <= i__2; ++i__) {
		    temp1 = 0.;
		    temp2 = 0.;
		    i__3 = *k;
		    for (l = 1; l <= i__3; ++l) {
			temp1 += a[l + i__ * a_dim1] * b[l + j * b_dim1];
			temp2 += b[l + i__ * b_dim1] * a[l + j * a_dim1];
/* L220: */
		    }
		    if (*beta == 0.) {
			c__[i__ + j * c_dim1] = *alpha * temp1 + *alpha * 
				temp2;
		    } else {
			c__[i__ + j * c_dim1] = *beta * c__[i__ + j * c_dim1] 
				+ *alpha * temp1 + *alpha * temp2;
		    }
/* L230: */
		}
/* L240: */
	    }
	}
    }

    return 0;

/*     End of DSYR2K */

} /* igraphdsyr2k_ */

